First, knead the dough from the flour, eggs, oil and salt in a deep bowl. Leave the dough to rest for about 15-20 minutes and roll it into a long strip. Cut pieces as large as your pan in which you will prepare the lasagna. Heat oil in a frying pan and add the onion to fry. Add the minced meat and garlic. Cook the meat for about 20 minutes until it gets a nice brown color. Then add the tomato sauce and cook for another 20 minutes. At the very end, add the butter, salt and ground black pepper. In a baking pan, place a thin layer of the minced meat mixture, place a layer of lasagna leaves, again a layer of minced meat, béchamel, grated Parmesan and repeat the procedure. Layer of lasagna leaves, minced meat sauce, béchamel and grated Parmesan. Finally, finish with a layer of lasagna leaves, minced meat sauce, a little béchamel, grated Parmesan and grated yellow cheese all over the pan. Bake in a preheated oven at 180 degrees for about 30 minutes.